Once, there was a struggle between two races. The "Erma" tribe, who have lived in the forest since ancient times, lived peacefully. One day, however, the Otta invaded the forest. The Otta tribe cut down the trees in the forest and captured the Elma tribe. The Elma tribe, utilizing the resources of the forest, oppose the Otta tribe. This is a board game for two players only. Players fight for the survival of their own tribe as either the Otta or the Elma. The Otta tribe invades the forest where the Elma tribe lives, while strengthening their own power. The Elma build treehouses and traps to defend their forest against the Otta invasion. The goal of the Otta is to annihilate the Elma, while the goal of the Elma is to survive. The game is asymmetrical, so there are different things to think about depending on which tribe you are playing. This game is recommended for those who like to think about where to move their frames on the game board and how to strengthen their own power in short rounds. In the later stages of the game, there is more to do and more to think about.